As part of the "Chipmunks" Team within Gator Theme Park Engineering and Design's Interactives Design Team, I applied and further developed my Arduino prototyping skills to create a knocking pattern detection system to activate our team's two interactives.
The goal of the team was to design and prototype two Wild West-themed, small-scale interactives with similar activation methods. I developed the idea of having different knocking patterns to activate the devices. Together, we brainstormed different interactives and decided on (1) a bartop where the user can tap in front of them in a certain pattern and have a drink automatically slide down to them and (2) a saloon door that when knocked on in a certain pattern would open to dancing chipmunks.
To make the detection system, a type of sensor was needed to detect a "knock". I investigated capacitive touch, piezoelectric, and piezoresistive sensors and compared their activation ranges and units. For the purpose of detecting a "knock" (a forceful hit on a surface), I selected a piezoresistive sensor to reduce noise and get stable maximum force readings of the knocks.
I then created a prototype circuit using an Arduino Uno and breadboard with the piezoresistive sensor. To detect the pattern, I had the Arduino read the sensor's analog signal, check if the values are within thresholds, and compare the intervals between valid taps to a predefined "pattern library" that contains arrays of accepted patterns. If a pattern is detected, a function was called that would activate the appropriate interactive. After testing and refining the maximum and minimum force thresholds, additional limits to filter out false positives were added. These include a timeout to restart pattern detection, max tap duration to prevent detection of objects resting on the sensor, and debounce delay to prevent knocks from being registered twice due to noise.
The detection system was fully implemented into the final saloon door interactive prototype (full prototype demo shown below). The bartop interactive is still in-progress to complete the mechanical movement system (circuit demo of motor activation shown below).